Muncaster's Joys Valve Engine

[Florian Eberhard]

but I'm still kicking myself over the bearing!

Hi Simon

Thats normal - we all do things like that - because it is in our mind that a reamer must give a good finish.
Guess how many times I used a reamer for "finishing" but the bore turned out not to be as I excepted it. I could have kicked my a** quite a few times for that!!

Florian

[NickG]

I struggled with my crankshaft too Simon, I actually started down the loctite route but I got too slack a fit and the loctite didn't cure so ended up trying to pin it but it had a wobble so ended up trying to silver solder using the lathe as a jig. Just a total nightmare, I've made ones
Just with loctite and no pins for my flame gulpers which worked perfectly but a lot less force going through those.

[sshire]

Simon
First rate, as usual. I generally categorize mistakes as a "character building experience." My philosophy is that it's only a bit of metal and I can make another (unless it's the last hole to be tapped in 2 6-hole bolt circles in a part that took 2 days to make and the 1-72 tap breaks. DAMHIK)
I've had very good results with built-up crankshafts. A few are roll-pinned and Loctited, but recently I've gone to tiny taper pins. Very solid and removable.

[smfr]

I had a terrible experience with the latest silver-soldering attempt (which I'll document once I have some actual progress to make up for it!) so it's going to be Loctite and taper pins. I'm currently trying to figure out how to attach the counterweights, or just make them part of the throws.

Simon

[smfr]

Now that I've made a bit of progress on a good-looking crankshaft, I'll show you what happened to the earlier attempt.

You may recall that I made a "practice" crankshaft with a single silver-soldered throw, so I decided to have another go at silver-soldering on the second throw. This time, I left the journal rod much longer, so I could use a couple of fixture to hold it parallel to the main shaft, but I think this cause more problems than it solved...

Here it is set up with flux for soldering; I tried the "add the solder while hot" rather than using pre-formed rings:



But after overly-prolonged heating with my single propane torch, I couldn't get it hot enough for solder penetration:



What a mess! I think the added mass of the longer journal rod took it beyond the capabilities of my torch.

Time for a rethink 

Simon

[smfr]

My second option was Loctite and pins. I'm hoping this will be the real deal this time, so I spent a bit more effort on the parts.

First, a bit of 1-1/2" x 1/4" gauge plate was marked out for four throws with counterweights, here nicely illuminated by my new IKEA LED lights  (which make photography easier too  )



I drilled the journal holes in increments up to 31/64", then bored off a few thou to make sure the hole is straight:



then reamed with a nice USA-made 1/2" reamer that replaces the one that made a mess of my bearings  The holes turned out to be a nice snug fit to the 1/2" drill rod I'm using for the shaft and bearings.

Excess material was trimmed away on the bandsaw in vertical mode:



and the throws ganged together in pairs for trimming on the mill:



You never know when a previously-made angle is going to come in handy 



So we have two pairs of throws in the rough:



Next the counterweight ends were radiused on the rotary table:



and the journal ends also; easy because everything is rotating around the shaft hole, located in the center of the table via a bit of 1/2" rod in a collet.

I put a rather timid bevel on the counterweights with a countersink:



and probably should have made it more obvious  .

The shoulders needed a bit of rounding off, which was tricky to do with files because there's not much space to manoeuver, so a previously ground-down corner-rounding endmill was pressed into service, a bit too eagerly as you can see by the slight extra shoulder in the photo:



After some amount of filing and rubbing on wet & dry paper on the glass plate, we end up with two pairs of throws:



This post is getting a bit long, so I'll continue in a new one.

Simon

[smfr]

The shaft and journals are 1/2" O-1 drill rod (silver steel in the UK?). The reamed holes in the throws are a snug fit on these, so I turned a couple of shallow grooves to give the Loctite a bit of room to do its stuff:



and now we're ready for a mock assembly to make sure everything is on hand before applying the Loctite; note the spacer between the throws to keep them the right distance apart.



I used Loctite 603 (high strength, small gaps, no need to handle high temperatures). I did the four joints of one pair of throws at the same time, which was possibly a mistake; once you apply this stuff, it gets everywhere and blind panic sets in as your carefully-arranged setup gets knocked over as you try to get the parts in the right place before it sets up 

I managed to get the first pair of throws done, and after an hour or so for that to harden up, built a setup for the second set of throws, which was a little more elaborate 



The 1-2-3 blocks keep the second set of throws at 90deg from the first and that adjustable parallel in the middle is setting the spacing between the throws. Again, a mad scramble to get everything set up with the Loctite, and then working loose the bits that aren't supposed to be stuck to the throws 

After curing overnight, things look fairly respectable:



Now, to the pins. The plan here was to make tapered pins to match the taper pin reamer I got for this purpose, so I turned some pins from 1/8" O-1 with a taper using the topslide:



then drilled through the throws with a drill the size of the small end, and drilled half-way through with a slightly larger drill:



Here's the reamer, an import #4/0 taper pin reamer:



I started it in the chuck at low speed and light pressure, then recalled that these should be driven by hand;



but wasn't getting anywhere with that; it seemed to get stuck. I went back to reaming under power, and not surprisingly the inevitable happened and the reamer broke:



  Luckily I was able to knock the broken end out of the part from the other side. I obviously wasn't doing it right, but what's the right way to use a taper pin reamer? It seems like it's going to be cutting along its whole length once the hole steps are taken off, which, for an HSS tool less than 1/8" in diameter, seems like a lot of cutting pressure.

So, on to the backup plan, which was simple 1/8" reamed holes, which went just fine:



I resisted the temptation to deburr the holes; doing so would leave a bevel which would be visible after finishing.

I parted off the pins for these holes from 1/8" stock, then inserted them with a light coating of Loctite:



and peened the ends of the pins slightly:



When doing this it's important that the other end of the same pin is bearing the load on the anvil; you're trying to peen the head of the pin, not knock it out!

After a bit of time for the pins to set up, we can now cut off the excess journal material in the bandsaw, being really careful to catch the blade before it falls down and ploughs through the main shaft 



after which the journal ends can be tidied up by side milling:



followed by a bit of filing (the red pen shows what's being taken off):



Likewise the pins are taken down:



and finished with filing. Almost invisible!



So that's where I'm at for now. Tomorrow comes the slightly scarey part, which is chopping out the shaft sections for each throw. Fingers crossed!

Simon

[fumopuc]

Hi Simon, good to to see that you are back on the road with the Loctite solution. To avoid this silver solder mess, I have bought some time ago a cheap laser thermometer/ pyrometer  with a range up to 900° Celsius. Now I am able to check the temperature in the whole workpiece before I start a soldering. This was big a progress in my soldering procedure, so I have never tried again a soldering before the right temperature was there.

[sbwhart]

Bin quietly following you build Simon your doing some great work.

I much prefer the Loctite and pin method against silver soldering you end up with a far neater job and more than strong enough to function correctly.

Luckily I was able to knock the broken end out of the part from the other side. I obviously wasn't doing it right, but what's the right way to use a taper pin reamer? It seems like it's going to be cutting along its whole length once the hole steps are taken off, which, for an HSS tool less than 1/8" in diameter, seems like a lot of cutting pressure.

I also struggle to use taper reamers and run into similar problems to you Simon can't figure out what I'm doing wrong so if any of you guys have any tips they will be much appreciated.

Stew

[zeeprogrammer]

Good posts there Simon.
Good learnings and good progress.

What end of the pin did you mill down? Just the one opposite the end you peened? Or both? (Cause I'm wondering why you peened.)

[kvom]

That's the way I would do it too.  My preference is Loctite 620 (green), which is an anaerobic formula that sets only when there is no air.  Using this, the grooves you turned in the shafts would be counterproductive.  Any excess on the outside of the joints remains liquid and is easy to wipe off.  It's also strong enough that pins are not really needed.  The full size model uses .75" rod; the larger the diameter being used the stronger the bond.

[Jasonb]

Just need to bear in mind that the bond area my go up by the square but the capacity goes up by the cube so there will be more power being put into the joints on the larger engine. Also depends if you are just going to have it ticking over on air or put 120psi plus of steam through it to get the compounding to work and have it doing some real work.

J

[Kim]

Wonderful post Simon, and great progress!  Sorry about your problems with the tapered reamer.  I have no meaningful suggestions, but can relate! Feels awfully familiar!    I'm sure you'll let us know if you come up with the answer to this one.

Good backup plan with the straight pins though.  Seems like that will be a more than adequate solution for your situation.  And your crank is looking great!

BTW, what do you use for a heat source for your silver soldering?  What kind of torch do you have?

Thanks for your excellent post!
Kim

[smfr]

Thanks for the comments, everyone!

What end of the pin did you mill down? Just the one opposite the end you peened? Or both? (Cause I'm wondering why you peened.)

Zee, the peening is really just to get the pin to fill the hole, so that the join becomes almost invisible after cleanup. I peened both ends, and milled off and filed both ends, so the pins just disappear. (I rather liked the look with the pins visible though!).

Kvom, 603 is very similar to 620, but is better for press fits (up to 0.005" gap), and is more tolerant of oil remaining on the parts (according to a handy chart that I can no longer find online  ). Although now I read the chart, 680 may have been a better choice ("resistant to dynamic, axial and radial loads"). I think we're splitting hairs here though!

Jason, I realize these cranks will take some stress if I ever run this at high speed under steam; I'm a bit concerned that, by drilling 1/8" holes, I didn't leave much meat on the throws around the journals. At least this is a part that can always be made again if necessary without affecting other parts! BTW, this isn't a compound, just a straight 2-cylinder.

Achim, I've thought of investing in a laser thermometer. A quick search on Amazon suggests that ones that go into the silver-soldering range are over $100; if it works at food temperatures too, maybe I can persuade my wife to invest in one

Simon

[smfr]

BTW, what do you use for a heat source for your silver soldering?  What kind of torch do you have?

Kim, it's like this: http://www.amazon.com/ACE-AC25-TORCH-KIT7PC-PROPANE/dp/B0044FYTEU/ref=sr_1_22 but about 20 years old from an estate sale

Yes, I should probably invest in something beefier.

Simon